In recent years, high-end projectors utilize laser elements and wavelength-converting devices as illumination systems. The conventional wavelength-converting devices can be classified into two kinds of wavelength-converting device, one of which is a rotational phosphor wheel, and another one of which is a fixed phosphor plate module.
Please refer to FIG. 1 and FIG. 2. FIG. 1 schematically illustrates the structure of a rotational phosphor wheel of prior art. FIG. 2 schematically illustrates the structure of a fixed phosphor plate module of prior art. In a rotational phosphor wheel 1, phosphor powder (or phosphor agent) 11 is mixed with adhesive glues and coated on a specific position of the high-reflective substrate 10, which is circle-shaped. The high-reflective substrate 10 is installed on a motor 12, so that the heat-dissipation may be implemented through rotating by the rotational phosphor wheel 1 during performing wavelength conversions. On the other hand, since the heat-dissipation cannot be implemented through rotating by the fixed phosphor plate module 2, the phosphor plate 21 is generally mounted onto a surface of a high-reflective substrate 20, and a heat sink 22 is mounted on another surface of the high-reflective substrate 20. Under this circumstance, the heat generated by the laser source may be dissipated.
However, in the rotational phosphor wheel 1, the converting efficiency of phosphor powder 11 is low because of low reliability and low thermal conductivity of adhesive glues. Meanwhile, the rigidity of the high-reflective substrate 10 may be not enough to be applied through rotation and shake. In addition, in the fixed phosphor plate module 2, the heat-dissipation of the heat sink 22 is mainly implemented through conduction and convection, so the high-reflective substrate 20 and the heat sink 22 have to be chosen from components having relatively larger surface area. That is, the space requirements often exceed expectations. Furthermore, the phenomena of hot spot and heat diffusion causes high manufacturing cost and difficulty of the fixed phosphor plate module 2.
There is a need of providing an illumination system and a wavelength-converting device thereof to obviate the drawbacks encountered from the prior art.